1. Field of the Invention
The present disclosure relates to a bicycle, more particularly to a bicycle freecoaster hub.
2. Description of the Related Art
In a so-called freecoaster hub, a clutch member is driven by the chain sprocket to move axially along an axle, and while a pedal of a bicycle is pushed to drive the chain sprocket to rotate forward, the clutch member is driven to form an engagement state with the hub shell and, at this time, the hub shell and the chain sprocket can be rotated simultaneously. When the pedal is slightly pushed reversely to drive the chain sprocket to rotate in reverse, the engagement state between the clutch member and the hub shell will be released and, at this time, the hub shell can be freely rotated.
In order to ensure the clutch member is initially only axially movable along the axle and not rotated with the chain sprocket before the clutch member is engaged, a resistance unit is usually disposed between the clutch member and the axle to provide a resistance effect on the clutch member. For example, U.S. Pat. No. 7,712,593 disclosed a freecoaster hub including a plurality of springs and a plurality of steel balls built in an axle thereof. Cooperation of each steel ball and elastic action of the spring can apply resistance on the clutch member. However, the relationship between the clutch member and the steel balls is a high stress point-contact. On the one hand, the surface of the clutch member is easy to be worn by the steel balls, and on the other hand, the resistance provided by the steel balls is not consistent for the clutch member, resulting in that transmission failure may be occurred to impair stability of the driving power transmission during operation of the clutch member.
In addition, in order to meet different rider's demands, the clutch must have an adjustable stroke (i.e. distance of pushing the pedal). In aforesaid prior-art patent, for adjusting the stroke of the clutch, the user must insert a screwdriver into the axle to rotate the screw, to enable the screw to drive a rod to move axially along the axle, and a bolt will be pushed during the movement of the rod. The bolt is radially inserted into an adjusting ring to be mounted on the adjusting ring, so the adjusting ring is also pushed toward the clutch simultaneously while the bolt is pushed, resulting in that a distance between the adjusting ring and the clutch is shortened and the effect of adjusting the stroke can be achieved. Obviously, the prior-art patent has a problem of complicated structure. In addition, the axle of the prior-art patent must be performed a specific process for cooperation with the screw and the rod, and it causes more process cost and also negatively affects the structural strength of the axle. There is still plenty of room for improvement in the whole structure of the existing bicycle freecoaster hub.
On the other hand, in aforesaid prior-art patent, the hub shell and the axle are assembled together by several ball bearing units. However, the general ball bearing units have insufficient location and therefore capability in bearing an axial load, so if the hub is born an axial load exceeding the acceptable range of the smaller ball bearing units during the operation, the ball bearing units may easily be damaged, and structure of the chain sprocket or other component may possibly be affected.